Anyone used a Genesis 1,2 or 3 as a RGB to NTSC converter?

[master higgins]

Hi. I want to know if someone has used one of these consoles as a rgb to ntsc converter. I'm asking this because I can output 15khz horizontal frequency resolutions with my vga card, but obviously the signals are splitted (in red,green,blue, hsync and vsync). I was wondering if just soldering the pins 1 (red), 2 (green), 3 (blue), 6 (red gnd), 7 (green gnd), 8 (blue gnd), 10 (sync gnd), 13 (hsync) and 14 (vsync) and +5V to the proper pins of the chroma encoder (be it a cxa1145 or a cxa1645) would make it convert the signal to composite video.

I don't have a genesis on hand, so if anyone has made this experiment, feel free to answer!. To make your vga card emit 15khz modes, you can use winmodelines. It's in spanish, but it's self intuitive, you just have to paste one of these example modes in the big textarea and push "actualizar registro" (update registry)

Code: Select all

Modeline "240x240@60,0Hz 15,7KHz (60Hz)" 5.160 240 266 290 328 240 241 244 262  -hsync -vsync   
Modeline "256x224@64,0Hz 15,7KHz (64Hz)" 5.540 256 283 309 352 224 225 228 246  -hsync -vsync   
Modeline "256x240@60,0Hz 15,7KHz (60Hz)" 5.530 256 283 309 352 240 241 244 262  -hsync -vsync   
Modeline "256x256@55,0Hz 15,7KHz (55Hz)" 5.540 256 283 309 352 256 258 261 286  -hsync -vsync   
Modeline "288x224@64,0Hz 15,7KHz (64Hz)" 6.170 288 319 348 392 224 225 228 246  -hsync -vsync   

Then you reboot and run the winmodelines program again. Select one of the modes in the textarea and push "probar modo" (test mode). A messagebox will appear telling you that unless you have rebooted the PC, you cannot test new modes. Since you rebooted just press ok ("aceptar") and it will change the resolution. From now on the PC monitor will be out of sync, and you must connect the modded vga cable (with its pins soldered to the cxaXXXX) to the vga port and connect the composite output and the ground properly connected to an rca plug to the TV. If you can see the desktop crearly in color then it means it works. If you cannot see anything, just press the "esc" key in the keyboard to return to the previous mode.

If anyone is willing ot do that to his/her old genesis, I'd appreciate it so much.

Thanks for your patience

PS: I almost forgot it. With the cxa1145 i suppose you must connect the pins this way:

vga pin 1 -> IC's pin 2
vga pin 2 -> IC's pin 3
vga pin 3 -> IC's pin 4
vga pin 13 and 14 -> IC's pin 10
IC's pin 15 -> IC's pin 17
IC's pin 16 -> IC's pin 18
RCA plug positive -> IC's pin 20
+5V -> IC's pin 19 and 12
vga pin 6,7,8,10, RCA plug gnd and power supply gnd -> IC's pin 1 and 24

For the cxa1645, it should be the same, except that pins 15,16,17 and 18 of the chip are not used.

If any tech has any comment (like missing connections or components, please post)

[jaimegmr]

why use the genesis when you can just buy the chip by itself and build a separate circuit with it?

[master higgins]

Because that chip is a pain in the a** to find here in Chile, and the only way to get it is buying an old genesis (the psx prior to the scph5500 and the fctwin also has it)

I tried building a circuit with the AD724jrz IC, but nothing worked, and I think that the chip might well be fried (too much temperature from the soldering iron, a short i made while building the circuit, and so on). Also, the AD724 is SOIC, which is very difficult to handle.

I just wanted an easy way to use one of these consoles and make the converter, because all parts are well soldered and what would I need is just know which pins, joints or whatever where to put the signals.

Thanks for your attention!